In an electric motor including a commutator, a driving current is supplied through a brush to a rotor including the commutator. Hereinafter, an electric motor including a commutator is also referred to simply as an electric motor.
The electric motor has a contact point at which a brush and a commutator are in mechanical contact with each other. The commutator includes a plurality of commutator pieces. The electric motor uses the brush and the commutator to commutate a driving current that is supplied to a rotor. At the mechanical contact point, spark discharge occurs between the brush and the commutator in commutation of the driving current.
Methods for eliminating the spark discharge have been heretofore proposed. Patent Literature 1 describes a method using a variable resistor (hereinafter, referred to as a “varistor”) as and a method using a multilayer chip capacitor (hereinafter, referred to as a “capacitor”) as an element that absorbs a surge.
FIG. 7A is a plan view of a varistor to be attached to a conventional commutator. FIG. 7B is a sectional view showing a cross-section taken along line 7B-7B shown in FIG. 7A.
FIGS. 8A to 8D are main part conceptual views showing a mounting state of a conventional commutator.
FIG. 9A is a plan view showing a mounting state of a capacitor to be attached to a conventional commutator. FIG. 9B is a side view showing a mounting state of a capacitor to be attached to a conventional commutator.
FIGS. 10A to 10D are main part conceptual views showing a mounting state of a conventional commutator.
As shown in FIGS. 7A and 7B, varistor 20 has a ring shape as an outer shape. As shown in FIGS. 8A to 8D, varistor 20 is connected directly to commutator 1001 by solder 23.
As shown in FIGS. 9A and 9B, capacitor 21 is electrically connected to wiring plate 22 by solder 23. As shown in FIGS. 10A to 10D, wiring plate 22, to which capacitor 21 is attached, is connected to commutator 1001 by solder 23.
In other words, capacitor 21 is connected indirectly to commutator 1 through wiring plate 22. Capacitor 21 is electrically connected at such a position that a pair of adjacent commutator pieces are connected to each other.